The main objective of the Harvard Study of Adult Development is to understand successful aging. The project will continue a life course study of two socially contrasting cohorts totaling 724 men who have been prospectively followed by interdisciplinary study for 60 years (attrition has been held to 0.2 percent/year): A. The COLLEGE sample includes 268 men selected as sophomores in 1939-1942 for mental and physical health and high achievement. At an average of 81, these men are demonstrating marked longevity. B. The CORE CITY sample includes 456 men selected in 1940-44, at age 11-15, by the Gluecks as nondelinquent controls for their study of delinquency. They were from inner-city schools in high-crime neighborhoods. MAJOR OBJECTIVES over the period 2003-2008 will be: 1. To identify the developmental factors that predict adaptive aging in the 8th and 9th decades of life. 2. To identify predictors of marital functioning in late life, as well as links between marriage and healthy aging among the elderly. METHODOLOGY over the 5-year period, 2003-2008: The Study will continue to exploit the power of a multivariate, multimethod, prospective design. Major variables are assessed using questionnaire, physical examination, interview, and new observational and daily diary methods. 1. Contact will continue to be maintained with the entire sample by means of biennial questionnaires, and new daily telephone diaries will be used to assess emotional and physical well being, social adjustment, and instrumental activities of daily living over 8 consecutive days. 2. Physical examinations and telephone cognitive status examinations are obtained every five years. 3. For the estimated 100 COLLEGE and 100 CORE CITY men who are currently married and likely to give informed consent, marital quality and functioning will be assessed using a videotaped marital discussion between husbands and wives, along with individual interviews with each partner about the marriage. Parallel data (including daily diary data) will be collected on husbands and wives.